A few days ago I came upstairs to:
Me: how did you get in there?Nora: all by myself!
Either we needed to be done with the crib, which had a good chance of much less sleeping at naptime, or we needed a taller crib. This is also something we went through when Lily was little, and that time what worked was removing the bottom of the crib.
It's a basic crib, a lot like this one. The mattress sits on a metal frame, which attaches to a set of holes along the side of the crib. On it's lowest setting, the mattress is still ~6" above the floor. Which means if we remove the frame and sit the mattress on the floor, we gain ~6".
Without the mattress weighing it down, though, the crib would not be hard for an energetic toddler to tip. I've attached it to the wall on two sides with strapping, right into a stud:
Nora was eager to give it a try, holding on the rail and bouncing hard:
This should get us a bit more time with solid naps!
(I was going to do something similar with Anna when she was the same age, but the crib we happened to be using for her was designed differently and had a structurally important bar across the bottom.)